Orientated construction of visible-light-assisted peroxymonosulfate activation system for antibiotic removal: Significant enhancing effect of Cl.

Antibiotic contaminants can migrate over long distances in the water, thus possibly causing severe detriment to the environment and even potential harm to human health. Heterogeneous activation of peroxymonosulfate (PMS) assisted by visible light is an emerging and promising technology for the purification of such wastewater. This study designed an ultra-efficient and stable PMS activator (FeCN) to restore the typical antibiotic-polluted water under harsh conditions. About 90.94% of sulfamethoxazole (SMX) was degraded in 35 min in the constructed FeCN+PMS/vis system, and the reaction rate constant was nearly 50-fold higher than direct photocatalysis. Electron spin resonance, quenching experiments, LC/MS technique, eco-toxicity assessment, and density functional theory validated that the SMX removal was dominated by the attack of h+, •O2- and 1O2 on the active atoms of SMX molecules with high Fukui index, presenting as a simultaneous degradation and detoxification process. Such a visible-light-assisted PMS activation system also had good resistance to the environmental water bodies and a broad spectrum in the degradation of various pollutants. In particular, Cl- (50 mM) could significantly accelerate the removal of SMX with a 32.6-fold increase in catalytic activity, and the mineralization efficiency could reach 56.6% under identical conditions. Moreover, this Cl- containing system excluded the degradation products of disinfection by-products, and such a system was also versatile for different contaminants. This work demonstrates the feasibility of the FeCN+PMS/vis system for the remediation of antibiotic-contaminated wastewater in the presence and absence of Cl-, and also highlights their great potential in WWTPs.

Dual-quantum-dots heterostructure with confined active interface for promoted photocatalytic NO abatement.

Constructing heterostructure is an effective way to fabricate advanced photocatalysts. However, the catalytic performance of typical common multi-dimensional bulk heterostructure still suffers from the limited active interface and inefficient carrier migration. Herein, we successfully synthesize the SnO2/Cs3Bi2I9 dual-quantum-dots nanoheterostructure (labeled as SCX, X = 1, 2, 3) for efficiently and stably photocatalytic NO removal under visible light irradiation. The NO removal rate of SC2 is almost 8 and 17 times higher than that of the single SnO2 and Cs3Bi2I9, respectively. Moreover, the SC2 photocatalyst shows only 3 % attenuation after five consecutive cycles, demonstrating good photocatalytic stability. Systematic experimental characterization and theoretical density functional theory calculations revealed that the high activity and stability of SCX originated from the efficient charge transfer at the confined interface between SnO2 and Cs3Bi2I9 quantum dots. This work provides a new perspective for constructing innovative dual-quantum-dots nanoheterostructure and assesses their potential in photocatalytic environmental applications.

Identification of Halogen-Associated Active Sites on Bismuth-Based Perovskite Quantum Dots for Efficient and Selective CO2-to-CO Photoreduction.

All-inorganic Pb-free bismuth (Bi) halogen perovskite quantum dots (PQDs) with distinct structural and photoelectric properties provide plenty of room for selective photoreduction of CO2. However, the efficient conversion of CO2-to-CO with high selectivity on Bi-based PQDs driven by solar light remains unachieved, and the precise reaction path/mechanism promoted by the surface halogen-associated active sites is still poorly understood. Herein, we screen a series of nontoxic and stable Cs3Bi2X9 (X = Cl, Br, I) PQDs for selective photocatalytic reduction of CO2-to-CO at the gas-solid interface. Among all the reported pure-phase PQDs, the as-synthesized Cs3Bi2Br9 PQDs exhibited the highest CO2-to-CO conversion efficiency generating 134.76 µmol g-1 of CO yield with 98.7% selectivity under AM 1.5G simulated solar illumination. The surface halogen-associated active sites and reaction intermediates were dynamically monitored and precisely unraveled based on in situ DRIFTS investigation. In combination with the DFT calculation, it was revealed that the surface Br sites allow for optimizing the coordination modes of surface-bound intermediate species and reducing the reaction energy of the rate-limiting step of COOH- intermediate formation from •CO2-. This work presents a mechanistic insight into the halogen-involved catalytic reaction mechanism in solar fuel production.

Mechanisms of Interfacial Charge Transfer and Photocatalytic NO Oxidation on BiOBr/SnO2 p-n Heterojunctions.

In this work, hydrothermally prepared p-n heterojunction BiOBr/SnO2 photocatalysts were applied to eliminate NO in visible light. The as-synthesized BiOBr/SnO2 photocatalysts exhibit superior photocatalytic activity and stability through the establishment of a p-n heterojunction, resulting in a significant improvement in charge separation and transfer properties. The morphological structure and optical property of the BiOBr/SnO2 heterojunction were also investigated comprehensively. Extended light absorption into the visible range was achieved by SnO2 coating on the surface of the BiOBr microsphere through the constructed heterojunction between BiOBr and SnO2, thus achieving efficient NO removal. Moreover, the transfer channels and directions of charge at the BiOBr/SnO2 interface were determined by a combination of theoretical calculations and experimental studies. Within this p-n heterojunction, the charge in SnO2 migrates into BiOBr through the preformed electron transfer channels, thus generating an internal electric field (IEF) between SnO2 and BiOBr. Under the influence of IEF, the photogenerated electrons of BiOBr migrate from the conduction band (CB) to the CB of SnO2, thus promoting the separation of electrons (e-)-holes (h+) pairs. The intermediates and final products were monitored by the in situ DRIFTS technology in the process of removal of NO in visible light; hence, the oxidation pathways of NO were reasonably proposed. Meanwhile, the construction of the heterojunction not only achieves more efficient NO photocatalytic oxidation but also inhibits the production of more toxic NO2. This work provides mechanistic insights into the interfacial charge transfer for heterojunction photocatalysts and reaction mechanism for efficient air purification.

La-doping induced localized excess electrons on (BiO)2CO3 for efficient photocatalytic NO removal and toxic intermediates suppression.

Photocatalysis technology has been extensively adopted to abate typical air pollutants. Nevertheless, it is a challenge to develop photocatalysts aiming to simultaneously improve photocatalytic selectivity and efficiency. In this study, to improve the photocatalytic selectivity and the performance of (BiO)2CO3 in the oxidation of NO to target products (NO2- /NO3-), we developed a novel method to construct La-doped (BiO)2CO3 (La-BOC) for forming localized excess electrons (Ex) on (BiO)2CO3 surface. The results indicate that the Ex could effectively accelerate the activation of reactants and promote charge separation and transfer. Under visible light, the gas molecules could capture the Ex and get activated to produce reactive oxygen species (ROS) with high oxidation ability, which enables complete oxidation of NO to target products instead of producing other toxic by-products. Due to the functionality of the Ex, the photocatalytic selectivity and efficiency of La-BOC have been synchronously improved. Combining experimental and theoretical methods, this work unravels the pathway of charge carriers transportation/transformation and elucidates the photocatalytic NO oxidation mechanism. The present work could provide a novel method to improve photocatalytic selectivity and activity for safe air pollutant abatement.